The present invention relates to lasers, and more particularly, to a laser that is adapted for high-speed single mode optical fiber communications.
The main application for long-wavelength vertical cavity surface emitting lasers (VCSELs) is in high-speed single mode optical fiber-based communications. The key performance issues required for 1310 nm and 1550 nm single mode sources for optical communications are: single mode operation over a sufficient output power range (typically 1 mW) and wavelength and polarization stability over temperature and bias variations. In addition, the ability to tune the output wavelength is a highly desired feature for optical sources to be used in discrete wavelength multiplexed communications systems.
Tunable VCSEL sources in the 1310 nm and 1550 nm wavelength range are well known in the art. However, all of these devices are less than ideal. For example, one class of VCSEL is electrically pumped with the tuning realized using a movable membrane. However these devices have only been successfully demonstrated at 980 nm and 850 nm. At longer wavelengths, numerous technological difficulties have prevented commercial devices from being fabricated.
VCSELs that are optically pumped by 980 nm edge-emitting lasers are also known to the art. These devices are also tuned using a movable membrane. However, the cost associated with the multiple fiber to waveguide couplings and the cost associated with the 980 nm pump laser add to the cost of the device. As yet, the cost of these devices has prevented their commercial development for optical networks.
Fiber-Fabry-Perot Surface-Emitting lasers that are optically pumped with a pigtailed 980 nm laser have also been demonstrated. These devices are tuned via a piezoelectrically controlled cavity mirror. However, these devices are also economically unattractive because of the cost of the fiber to laser coupling and the extra cost of the fiber-coupled 980 nm laser pump.
Broadly, it is the object of the present invention to provide an improved long-wavelength light source.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.
The present invention is a light source for generating and coupling light from a first wavelength into an optical fiber. The light source includes an output laser having a first optical cavity that includes a bottom mirror located outside of the optical fiber, and a top mirror that includes a reflector located within the optical fiber. An active region between the top and bottom mirrors generates light of the first wavelength, preferably through optical pumping of an active region in the first optical cavity at a second wavelength. The reflector is preferably a Bragg reflector and may include a mechanism for altering the wavelength of the light reflected thereby as well as the distance between the top and bottom mirrors. A pumping laser that includes a second optical cavity having a top mirror, active region, and bottom mirror preferably generates the pumping light. The top mirror of the pumping laser is electrically connected to the bottom mirror of the first optical cavity, and the active region of the pumping laser generates light in response to an electrical current passing therethrough. The top mirror of the pumping laser may be located on an end of the optical fiber. Embodiments of the present invention in which the output laser is electrically pumped can also be constructed.